Its numbers go by position, and the positions differ between a plain track
and a switch. A switch made in the style of a plain track wrote them in the
layout of the plain one, so they were read back as other values: the up and
down part as the value of the path p3-p4, and so on.
The values are now one struct with pure functions to read, write and resolve
them, which replaces eight fields and which the unit tests can reach.